Funds are requested for the purchase of a single crystal X-ray diffractometer with a high power rotating anode generator and a low temperature accessory. A new X-ray facility in the Chemistry Department at Boston will greatly enhance the research progress of eight NIH-funded investigators. Currently, the chemists in the department interested in carrying out small molecule crystal structure determinations in the present facility sometimes encounter waiting times of three to four months. By the same token, the biochemists in the department who do large biomolecule structures develop large work backlogs when small molecule structures are being done. This proposal puts forth a solution to this dilemma, that being the purchase of a diffractometer to be dedicated for use by the small molecule chemists. An estimated 110 structures determinations per year will be carried out on the new instrument. Currently, there is diffractometer time for only about 20 small molecule structures. The existing facility will become dedicated for use by the biochemists in the Department, permitting them to keep up with their groups' demands for diffractometer time and thus dramatically enhance their NIH-funded projects as well. The programs funded by the NIH for the small molecule major user group include: l) synthesis of pradimicin A and related anti-HIV agents, 2) metal complexes of nucleotides and coenzymes, 3) catalytic and stereoselective C-C bond-forming reactions, 4) manganese oxo chemistry related to the water oxidation catalyst in Photosystem II, and 5) synthetic active sites for the catalysis of bond formation. The new x-ray facility will be housed within the Merkert Chemistry Center, and carefully operated and maintained by students and staff who will be trained for this purpose.